Generally, the pump of a waterjet propulsion system for a surface vessel is mounted in an opening in the transom of the vessel. Steering is provided by a steering nozzle that is mounted for pivotal movement about a substantially vertical axis in a position immediately aft of the discharge nozzle of the waterjet pump and is pivoted, usually by one or more hydraulic piston/cylinders that are coupled between the pump assembly or the transom and the steering nozzle. Upon actuation, the cylinder(s) pivots the steering nozzle to a selected position oblique to the axial such that the nozzle deflects the water jet to a direction having a lateral vector. The water jet is reversed by a reversing deflector that is normally positioned out of the path of the water jet for ahead propulsion but is moved, usually by a hydraulic piston/cylinder actuator, into the path of the water jet. Generally, the reversing deflector pivots about a horizontal transverse axis from an inactive position above or below the steering nozzle. The reversing deflector is shaped to turn the water jet to a forward direction.
The outboard location of the hydraulic piston/cylinders that actuate the steering nozzle and the reversing deflector requires that several hoses pass through openings in the transom, which complicates the construction of the transom and requires seals in each opening. If there is a failure of an actuator or a hose, hydraulic fluid is lost to the environment. The outboard actuator systems for the steering nozzle and the reversing deflector are also not easily repaired when the vessel is at sea.
Another previously known arrangement for actuating the steering nozzle and reversing deflector of a marine waterjet propulsion system, which is described and shown in U.S. Pat. No. 3,807,346, includes concentric shafts that extend vertically downwardly from a portion of the vessel hull that is located above the steering nozzle and reversing deflector, which are pivotally mounted on a bracket for rotation about a common vertical axis that coincides with the axis of the concentric shafts. The lower end of the inner shaft is coupled to the steering nozzle, and the lower end of the outer shaft is coupled to reversing deflector. The inner shaft is driven by a piston/cylinder steering actuator that is located within the vessel hull and is coupled by a steering lever to the upper end of the inner shaft. A piston/cylinder reversing actuator is coupled between the steering lever and the upper end of the outer shaft so as to pivot the reversing deflector relative to the steering nozzle.
The steering/reversing mechanism of U.S. Pat. No. 3,807,346 has the advantages of requiring only a single penetration of the hull of the vessel and of enabling the steering and reversing actuators to be located within the vessel hull, where they are protected from the hostile water environment and can be serviced readily. The rotation of the reversing deflector about a vertical axis is, however, highly disadvantageous, inasmuch as in the retracted position for ahead propulsion, the reversing deflector resides laterally of the steering nozzle where it creates a large drag. In addition, an inactive positioning of the reversing deflector laterally of the steering nozzle requires additional athwart-ship space, which is limited in many waterjet applications.